Arrangement and method for regulating asynchronous machines



Sept. 30, 1930. J OSSANNA Er AL ARRANGEMENT AND METHOD FOR REGULATING ASYNCHRONOUS MACHINES Filed Feb. 9. 1928 5 Sheets-Sheet 1 Sept. 30; 1930. J. OSSANNA ET AL 1,777,211

ARRANGEMENT AND METHOD FOR REGULATING ASYNCHRONOUS IACHINES Filed Feb. 9, 1928 5 Sheets-Sheet 2 F/gr 5 Sept. '30, 1930. OSSANNAET AL 1,777,211

ARRANGEMENT AND METHOD FOR REGULATING ASYNCHRONOUS MACHINES Filed Feb. 9. 1928 5 Sheets-Sheet 3 aum,Mh@,w-,mp-

Sept. 30. 1930';

J. OSSANNA E AL AR RAN GEI ENT AND METHOD FOR REGULATING ASYNCHRONOUS IACHINES magma. 9. 1928 5 Sheets- Sheet 4 lau- Sept. 30, 1930. 1 os s ETAL ARRANGEMENT AND METHOD FOR REGULATING ASINCIIRONOUS MACHINES Flied Feb. 9. 1928 5 Sheets-Sheet 5 Fig? 7.7

44444441 .nnpbunn Patented Sept. 30, 1930 UNITED STATES JonANn ossnmva AND HANS ennnnn,

OF MUNICH, AND FRITZ HOFMANN, OI

MUN IC H-TALKIRCHEN, GERMANY, ASSIGNORS TO SIEMENS-SCHUCKERTWEBKE AKTIENGESELLSCHAFT, F BEBLIN-SIEMENSSTADT, GER-MANY, A CORPORATION OF GERMANY ARRANGEMENT ANDMETHOD FoRrREGULATING ASYNCHRONOUS MACHINES' Application filed February 9, 1928, Serial No.

' Our invention relates to a system for generating voltages of any desired magnitude and phasein circuits carrying alternating current of variable frequency.

In regulating asynchronous machines by.

means of commutator rear machines the task frequently arises to compensate the wattless resistance of windings which carry alterri eting current of variable frequency, as

7 already described in our prior American application for patent Serial No. 242,198of December 12, 1927. According to the said application a commutator machine driven with constant or substantially constant speed and a substantially non-reactive transformer, the secondary Winding of which feeds the exciter winding of the commutator machine are employed for the purpose. This arrange ment may, however, also serve to generate a voltage Which does not simply stand at right gles to the primary current, but encloses with it any desired angle.

The present invention refers to an arrangement and method for regulating the speed or also the phase compensation of asynchronous machines by means of so-called commutator rear machines, which are connected in cascade with the asynchronous machine.

The invention relates in particular to such regulating systems and arrangements in which a load current is a produced in the asynchronous machine which is mdependent of the slip, by introducing into the secondary circuit of the asynchronous machine and by way of the commutator machine two voltages, of which one neutralizes the secondary voltage of the asynchronous machine for each slip frequency, whereas the second voltage is independent of the slip and produces the load current.

The essential novel feature of the invention comprises a current transformer (in particular a variable phase transformer) which is connected with its primary winding into the secondary circuit of the asynchronous 253,111, and in Germany February 14, 1927.

cuit of the asynchronous machine by way of the commutator machine, neutralizes the induced stray voltage produced in the secondpanying drawings in Which- Figure l shows a portion of the total wiring arrangement comprising our invention, this portion illustrating the current transformer and the commutator rear machine connected according to the present invention, thereby illustrating the general principle involved;

Figure 2 represents a vector diagram of the voltages and currents produced, by the current transformer and introducedinto the commutator machine;

Figure 3represents avector diagramof the currents and voltages existing-in the multiphase current transformer;

Figure 3 represents the Wiring arrangement of the primary and secondary windings of the current transformer pertaining to the vector diagram, Figure 3;

Figures 4, 5 and 6 eachrepresent complete modified diagrams of, the system according to our invention;

Figures 7 and 8 represent vector diagrams of the currents and voltages in theasynchronous machine, and

Figures 9, 10, 11, 12 and 13 represent further modifications of the complete wiring diagrams according to the present invention.

Referring to Figures 1 and 2, the commutator machine 1 and the primary winding of the practically non-reactive transformer 2 are traversed by the current J of the frequency F l/r 31 w denotes in this case the frequency of the net voltage supplied to theasynchronous machine; with this fre-' quency corresponds the synchronous rotary speed of the primary flux of the asynchronous machine. a v on the other hand denotes the frequency to whichcorresponds the speed of the rotor of the asynchronous machine, and s represents the slip of the asynchronous machine in per cent. In the secondary winding of the transformer 2 a voltage E of the alternating induction is induced which lags behind the current J by 90 and thus assumes a phase relation indicated by the vector 7'.J in Fig. 2 of the drawings, provided the windings of the transformer are coaxial to one another. If, however, the secondary winding is turned through the angle a in relation to the primary one, which is possible in the case of a booster transformer, the voltage E of the. alternating induction will enclose the angle a with the vector j. J In Fig.2 it is assumed that the voltage E lags behind the vector j.J by the angle 0:. Equal in phase or at least approximately equal in phase with the voltage E is the exciter current J of the commutator machine 1, provided the ohmic resistance 3 in the circuit II is high in relation to the wattless resistance. The voltage U generated in the commutator machine is ultimately either equal in phase with the exciter current J 2 or encloses with it an angle of 180. It is thus possible to generate by means of the arrangement mentioned a voltage U which with respect to the current J encloses any desired angle (in Fig. 2 (90+a)). For the.

voltage E the vector equation chronous machine in which the rotor does not continuously rotate, but is merely shifted into the desired angular relation to the stator by any suitable outside means.

It is, however, also possible to set any desired angle between the current J and the voltage E by the aid of a static transformer. It is merely necessaryto divide the secondary vwinding into two or more portions and to connect them in suitable manner. In the primary winding are induced the three selfinduction voltages 1 E and E which enclose with one another an angle of 120. In the secondary winding, on the other hand, six voltages are developed (E E E E E and E if this winding consists of twoparts. The voltages E E and E are of equal phase. The resulting secondary voltages are indicated in the system of connection illustrated in the vector diagram Figure 3 and in the pertaining wiring diagram Figure 3 by Ea E1 2; b 2' 3; 1: 3 1 2 The vectors enclose with the primary voltages the angle a. By means of a static transformer anydesired phase displacement-n may thus be adpusted; the only difference 13 that a change of the angle a, if necessary, is not so easily carried out as with the boostertransformer.

If the frequency 11 v of the current passes through zero into the negative, if thus v be comes larger than 1 the direction of rotation of the rotating field in the booster transformer changes, so that the voltage E does no longer lag I behind the current J by (90 a), but by (90 a)". If a variation of the angle is not practicable when exceeding synchronism, it is necessary, for oversynchronism, to brmg the booster transformer 2 into a different position. This may be effected automatically, as fully explained in our above mentioned patent application. When an ordinary static transformer employed, however, a change in the connections becomes necessary for oversynchronism.

Only in the specific case in which-the angle a is zero, a change in the connections is not necessary. By the aid of the system of connections shown in Fig. 1 with all its varieties according to our application S rial No. 242,198 avoltage may be generated, which encloses with thecurrent not only an angle of but'any other desired angle.

It is furthermore possible to let the secondary windings of any numberof transformersact upon the eXciter winding of one and the same commutator machine and thus to generate different voltages in the said commutator machine which are in a definite ratio, regard ing magnitude and phase, to the primary currents of the transformers. For this purpose all the secondary windings of substantially non-reactive transformers are connected in the exciter circuit of the said coinm-utator machine. This is illustrated in Fig. 4 of the drawings. The slip output machine 2, as well as theexciter machine-3 of the said machine 2 are driven by a motor 4 of constant or substantially constant speed.

In the circuit II is connected the primary winding of the transformer 5 in the circuit III the primary winding of the transformer 6. The secondary windings of the transformers 5 and 6 work'on the circuit IV fed by the frequency converter 7. It is then nceessary to render the circuit IV non-inductive in any suitable manner, so that proportionality ex ists between the voltages mentioned and the current J This may be effected by connecting in circuit a non-inductive resistance 8 of suitable value. This-method has, how ever, the disadvantage of leading to high capacities of the transformers 5 and 6 and the .frequency, eme ted. Immead of.

cne flmg h Ohmic. resist nce the i duct-wig ofthecircuitIVma preferably be remov This may be effectetl by roviding a compen sated machine 9, a trans orrner 10 and a noninduetive resistance 11 i.'e. acoording... the

namely U34 j 3 ke s-r73 I U724 j s kg4-.ja.- I For the exciter current I; we then obtain under the assumption that. the. eircuitIV'has been rendered nonsinduetive, the equation:

in which nrepresents the ohmic resistance of circuit IV; Proportional to the-current J i s the voltage U 'of the commutator machin 3, so that we m.ay;write In this equation 0 represents a constant, determined by the dimensions of the commutator machine 3 by which constant the ratio between. the voltage induced in the commutator machine 3 and, its exciter -current are determined. On the other hand we have f with sk is denoted the resulting wattless resistance of the circuit III at. the slip frequency and n, represents, the ohmic resistance of this circuit. From this follows If We now make 6 Hind kgq kg 8 43 u we obtain The voltage U of the slip output machine :is proportionalto the .exciter current: J We thus obtain meant 10 or if We introduce forql and U the values from Equation 9 (or 3) U .[U5+-jsk 11 3-74 In the foregoing equation .0 denotes a-constant which, the same as the aforementioned constant 0 ,isdetermined by the dimensions of the machine. winch. furnishes the slip energy.

InthiseqHa iQQ 1 em e theprimaryleak: age-coeflieient and-g the ratio of the mdu gei By intr eucme the value U; imm Equfi lQn-ll .into-th sequetwn, es

knead. a are so. chnsentha thetwecqnstions:

are compl dxwithu Thi pr es. that by 5 1W solar s n ial y noneac ive .tmn ermels, th Pit mary indingso wh oh-are enn eted inthe rcuit II andlll of igi and. the seconda y nd ngs 0i whichw rk .on-the circuit W1 is, erexsmple, .pee iblo. oohtnie fer'the secondary current, J the simple relation. of the Equation 14,.

If new the secondary current J, 'changesin dependence of the slipxancl'Ut according to the Equation 14,it can-be proven; as will'be done further on,- that the effective out-put of the asynchronous-machine changes propoe tional to the slip, while the wattless output is practically independent :of the slip. As und cert in ci cum ta ces it m y e. esir b e that. h ffe tive output changes toa lesser degree, or, not t all, Withthe s ip, it w ll f rst be shown how this may be attained. We shall then-have an opportunityto show the application of the present invention by further examples.

In rder t e ependence otthe effective output: from thelip o o do. away with'it a1togethe;,-we are cempelled to introtransmission of the transformer 10.

duce into the circuit II' besides the voltages 8-E20 and in the rotor of the main machine from which an auxiliary voltage Uh can be derived which is determined by the equation -Ub=U +J .(r jska 16 when by I00 is understood a certain portion of the secondary wattless resistance of the leakage, so that 1 k0'2 ]C 0'2+]C0'2 If from Equations 12 and 16 U is eliminated,

L at 18 1 171 W1 2 The auxiliary winding and the main winding in the rotor are assumed to be coaxial.

In Fig. 5 of the drawings the first method is illustrated, how the auxiliary voltage Ub can be introduced into the circuit. Ul? is first brought to the network frequency 11 by a periodicity converter 9 to be then introduced into the circuit of the frequency converter 7 by a transformer 10. Since otherwise the i system of connections of Fig. 5 is identical with that according to Fig. 4, not taking into account that the slip output machine is now directly coupled withthe main machine 1, it is obvious that the results obtained up to now can also be transmitted to the system of connections of Fig. 5 by introducing into the Equation 14 in the place of U the new voltage In this ,u takes into account the ratio of Instead of Equation 14, we thus get the equation s.E U0+ m m -J 20 7'3.7"4 the fact that the slip output machine 2 possesses no longer a constant speed being neglected. If we now imagine the value Uh obtained from Equation 18 introduced into Equation 20 we see, that the desired proportionality between the current J and the resulting voltage in the circuit II is lost again. The auxiliary voltage Uh is thus not accurately the voltage which leads towards the desired aim.

It is, however, possible to render the voltage, with which the frequency converter 9 is fed, independent of current J by introducing a further voltage in the circuit V of Fig. 5. It is merely necessary to provide a further transformer 11 the primarywinding of which is traversed by the current J and the secondary winding of which is connected in the circuit V, in order to attain the desired aim. This has been done in Fig. 6. Otherwise this figure illustrates exactly the same system of connection as the Fig. 5 of the drawings.

The secondary voltage of the transformer 11 is i i U25 j8k2;5.c] V The resulting voltage with which the frequency converter is fed thus is V wbjb r w .f 2 U25 wzjz [SE20 I JmSll 61 kwlljl) then we have* wt. b

Ul? U25 Wi-SE If the other transformers 5 and 6 are chosen as stated hereinbeiore, we get instead of Equation 14 or 20 the equation $.E20 [U0 [725)] 7'2.j c 3- 4 V or with the values from Equation 24 If main and auxiliary winding in the rotor enclose between them and the angle 5 then we can make wbjb Ul? +UZ5= hy- .8.Eg0.e]5 24 so that instead of Equation 27 we obtain the equation 8.E20[1y cos 5-1}; sin 6];uz. ifo=raj 27 Frpliln this it follows that the wattless output may be made variable Wi s.

.The Equation 27 differs from Equation 14 by the factor 1-11 following s.E By a suitable choice of p, and .thusthe ratio" of transmission of the transformer 10, it is possible to make the influence of all) and J, as great or email as desired. At'u= 1 the equation'member which contains the factor c.15 disappears so that J, is entirely independent of the slip.

. At this place it may be pointed out that theflarrangement of the transformer 11 is. not at .all necessary in the wiring dia wam of Fig. 6 to attain the aim sought. It is. also possible to get along with the diagram, of connections of Fig. 5 by dimensioning the transformer 5 otherwise than stated.

. After the application ofour invention has been demonstrated above with reference to a few. examples, it will-now be proven that by the provisions madeit is. possible .to regulate at will the exchange of the effective output and the Wattlessoutput of .the asynchronous machine withthe network. For'the primary terminal voltage I l the equationholds good or if for the current J the value. from .Equation' 27 is introduced .k 1 1( '1 *J 1)+JT: l 2o( #1) M- ol 30 If r is neglected as snicll'in comparison with k1 (without this neglect a very similar-result is obtained) then we .get

If it is furthermore taken into; account that .1' uw if This equation is. graphically illustrated Figs. 7 and 8. J consists of three components, The first component is leading by in relationto the voltage U It represents the magnetizing current 'of'fihe asynchronousmachine. The second component is It isproportionalto the voltage U andrequal The third component is given by PEP-M U1 in phase with U but independent of the slip.

tween the slip and t e mponent fim y be varied at willby choosing aiproper value for At m=0the change of E'Pwiththe slip:is very great; at ,u l on the other hand P P is equal to zero. so that the effective component. of J is. perfectly independent of the slip. The wattless component of J is entirely independent of a. 'At synehronism (pointP wegetaccording to thephaseof U either motor action (Fig. 7) or generator action (Fig. 8) or a pure wattless current. The wattless current may. be regulated at will. by c... At undersynchronism in. the case-o Fig. 7 the negative effective current taken .absolutely'becomes greater, i. e. the output. of the .machinerunning as motor grows. .At. oversynchrc'nism the negative effective current .firstdrops back to. zerov then becomes positive (generator .action). 'IIJhis also applies to the caseillustratedin a manner it con'ldbe. att in d (see-footnote on. page 4) thatthe wattless output varies proportional. with the lip.- 1' To express it concisely, it isby the aid lofnur. invention possible .tojmpart to the. .asym chronons machine any desired characte istic,

as regardsthe effective output .as well as the wattless output.

' .Forthe sake of completenessjthe application of .ourinvention be sho n. incases in which the auxiliary voltage Ub is con nectedintothe. circnits.. in otherways. In

. Figs. 9 and '10 the auxihary voltage isemployed .ior the excitation of the compensated, machine 3., The exeitercurrent J 0 M ing from the auxiliary woltage is regulatedby a resistance 9. In both casesthe tr nsfmm one .5 and 6. work uponthe circuits .IV. The fr uency con-verter-,- whiclanlas be oompew sated. .or not compensatedis. entheother hand Fig. 9 -connected...in. the circuit 1H1 andin ,Fig. .10 in; the circuit 1V.

in .he systems of connection acco dingcto' the Figs. 11,.12and .13the auxiliary voltage is transformed by a transformer-9 the-ratio of transformation of which is variable, {and then connected either in the circuit III ,as in Fig. 11, .or in the circuit .IV, as in the Figs. .12 .md 13. In Eig. .12 -.the circuit lvismadanon.

inductive by a resistance 8, While in Fig. 13 the non-inductivity of the circuit IV is attained by an arrangement according to our prior application. for patent Serial No. 242,198. The Wiring in Fig. '11 has the disadvantage that at synchronism the transformer 9 is traversed on the secondary side by direct current. This is avoided in the systems of connection according to Figs. 12 and 13.

In conclusion it may be pointed out that thepractically non-reactive transformer could also be connected into the primary circuit in place of the secondary circuitof the asynchronous machine. It Would then have to Work on an asynchronous machine With the same slip frequency as the main machine and the voltage of this asynchronous machine would have to be introduced into any eXciter circuit.

Various modifications and changes may be made Without departing from the spirit and.

the scope of the invention, and We desire, therefore, that only such limitations shall be placedthereon as are imposed-by the prior art.

' We claim as our invention:

1. In combination an asynchronous machine, a commutator rear machine connected into the secondary circuit of said asynchronous machine, a current transformer connected With its primary Winding into the secondary circuit of the asynchronous machine, means for energizing the exciter Winding of said commutator machine by the secondary Winding of said transformer, said transformer being dimensioned and adjusted in its phase so that its secondary Winding introduces by Way of the commutator machine into the secondary circuit of the asynchronous machine a voltage, Which neutralizes in said secondary machine circuit the inductive stray voltage produced by the load current.

2. In combination an asynchronous machine, a commutator rear machine connected into the secondary circuit of said asynchronous machine, a rotary transformer con nected With its primary Winding into the secondary circuit of the'asynchronous machine, means for energizing the exciter Winding of said commutator machine by the secondary Winding of said transformer, said rotary transformer being dimensioned and adjusted in its phase so that its secondary Winding introduces by Way of the commutator machine into the secondary circuit of the asynchronous machine a voltage, Which neutralizes in said secondary machine circuit the inductive stray voltage produced by'the load current. 3. In combination an asynchronous machine,- a commutator rear machine connected in cascade With said asynchronous machine, means for producing in the commutator machine an eXciter field, consisting of tWo com.- ponents, of Which one is dimensioned in size and phase so that its'voltage, introduced by the commutator machine into the secondary circuit of the asynchronous machine, increases proportionate With the slip of said asynchronous machine and at least approximately neutralizes the secondary voltage of said latter machine, and the other component producing in the secondary circuit of said machine a load current Which is independent of the slip, a current transformer having its primary Winding connected in circuit With the secondary circuit of the asynchronous machine, means for feeding the eXciter Winding of the commutator machine by the secondary Winding of said current transformer, said current transformer being proportioned in size and adjusted in phase so that its secondary voltage introduces by Way of the commutator machine into the secondary circuit of the asynchronous machine a voltage, Which neutralizes in said secondary circuit the inductive stray voltage produced by the load current.

4. Method of generating in asynchronous machines a load current independent of the slip, consisting in supplying to the secondary circuit of said machine a plurality of voltages, of Which the first is dependent from the slip and for each slip equal and substantially opposite to the secondary voltage produced by the main field of the machine, the second voltagesupplied beingindependent of the slip and producing the secondary load current of the machine, the third voltage supplied being equal but opposite to the stray voltage produced in the secondary machine circuit by the load current therein for neutralizing said stray voltage.

5. In combination an asynchronous machine, a commutator rear machine connected in cascade With said asynchronous machine and having an exciter Winding in its stator and means for supplying a slip frequency voltage to said exciter Winding, a current transformer having its primary Winding con-' nected in the secondary circuit of said asynchronous machine, means for applying to the exciter Winding of said commutator machine the secondary voltage of said current transformer, said transformer being dimensioned in size and arranged in phase so that its voltage, applied to the secondary of said asynchronous machine by Way of said commutator machine, neutralizes the secondary stray voltage of the asynchronous machine pro duced by the load current, and means adapted to neutralize the inductive voltage produced in the eXciter Winding of said commutator machine.

6. In combination an asynchronous machine, a commutator rear machine connected in cascade With said asynchronous machine and having an eXciter Winding in its stator, a frequency converter adapted to supply a voltage of prevailing slip frequency to said eX- citer Winding and means for supplying net frequency to said converter, an auxiliary winding in the secondary portion of said asynchronous machine, means for applying the voltage produced in said auxiliary Winding and the slip frequency voltage of said converter to the exciter Winding of said commutator machine, a current transformer connected with its primary winding in the secondary circuit of said asynchronous machine, the voltage of the secondary transformer winding being applied to the exciter winding of said commutator machine, said current transformer being dimensioned in size and adjusted in phase so that its voltage, introduced into the secondary winding of the asynchronous machine by way of said commutator machine, neutralizes the stray volt- 1 age produced in the secondary Winding of the asynchronous machine by the load current in said winding.

In testimony whereof we aflix our signatures.

JOHANN OSSANNA. HANS GRANER. FRITZ HOFMANN. 

